A ProMED-mail post
<http://www.promedmail.org>
ProMED-mail is a program of the
International Society for Infectious Diseases <http://www.isid.org>
Date: Spring 2014
Source: Spud Smart [edited]
<http://www.spudsmart.com/past-issues/409-blot-on-the-landscape-spud-smart-spring-2014.html>
Researchers warn producers across the country not to underestimate the deceptive new strain currently dominating the late blight pathogen pool. For Alberta, until 2010 [see ProMED-mail post 20100915.3336] the province was virtually late blight-free. Lately, wet springs and high humidity -- uncharacteristic for this region -- have nurtured the growth and spread of the disease.
In 2013, for the 2nd year running, US-23 was the predominant late blight strain across Canada, confirms Khalil Al-Mughrabi, New Brunswick Department of Agriculture, Aquaculture and Fisheries.
Although pathogen populations can shift quickly, there's a good chance this strain will be showing up in 2014. Understanding the US-23 strain could save farmers from a nasty surprise at harvest or during the storage season.
US-23 entered Canadian fields in 2011 and has since displaced other strains. Plants infected by US-23 still present lesions on stems and leaves, however, the characteristics are different from older strains.
"In potatoes, you tend not to get as aggressive a disease in leaves and stems," says Rick Peters, Agriculture and Agri-Food Canada. But, "Unfortunately, it's very aggressive on the tubers. On the surface it looks not too bad, but suddenly at harvest there's major tuber rot."
Another difference between US-23 and US-8 -- the predominant strain [in Canada] from the mid-90s to around 2010 -- is its effect on tomatoes. US-8 was particularly aggressive on potatoes, whereas US-23 is especially aggressive on tomatoes. The specific characteristics of
US-23 have influenced disease management strategies. More collaboration between industries is needed, says Peters.
--
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[Potato late blight (PLB) is caused by the fungus-like organism _Phytophthora infestans_ and can cause 100 percent crop loss. The pathogen can also affect tomato and some other solanaceous crops. In potato, it affects leaves as well as tubers, and in tomato, it causes lesions and rotting of leaves, stems and fruits. The disease can spread rapidly within a crop and destroy it within a few days. Under favourable conditions, epidemics in tomatoes may be even more rapid than in potatoes.
PLB is spread by plant material (including plant debris and volunteer crop plants), mechanical means (including human and insect activities), wind and water. Disease management requires an integrated approach and may include removal of pathogen reservoirs, crop rotation, preventative fungicide treatments of planting material (potato seed tubers, tomato transplants) and fungicide sprays of crops. However, more virulent strains with additional fungicide resistances and increased yield losses are emerging frequently.
Late blight is considered an increasing problem worldwide and seed tuber certification schemes have been set up in many countries as an important part of PLB management. Development of resistant cultivars is being counteracted by the adaptability of the pathogen. Clean planting stock (potato seed tubers, tomato explants) and management strategies for fungicide resistance of the pathogen are therefore considered vital to control PLB outbreaks in the future.
Maps
Canada:
<http://www.lib.utexas.edu/maps/americas/canada_pol_1986.gif>
Individual provinces via:
<http://atlas.nrcan.gc.ca/site/english/maps/reference/provincesterritories>
Pictures
Late blight on potato:
<http://www.potatomuseum.com/images/exblightfieldwithinsert.jpg> and <http://www.concordma.com/blog/Symptom_potato_late_blight.jpg> (leaf) Late blight on tomato:
<http://ipm.illinois.edu/ifvn/volume15/images/tomato_late_blight.jpg>
Microscopy of PLB infected cells:
<http://micro.magnet.fsu.edu/optics/olympusmicd/galleries/brightfield/images/potatoblight.jpg>
Links
Late blight fact sheets:
<http://ohioline.osu.edu/hyg-fact/3000/3102.html> and <http://vegetablemdonline.ppath.cornell.edu/factsheets/Potato_LateBlt.htm>
Disease history and background:
<http://www.apsnet.org/edcenter/intropp/lessons/fungi/Oomycetes/Pages/LateBlight.aspx>
Late blight information and resources via:
<http://euroblight.net/>
PLB strains in North America:
<http://www.dupont.ca/en/products-and-services/crop-protection/vegetable-protection/articles/late-blight.html>,
<http://peicanada.com/west_prince_graphic/publication/
new_strain_late_blight_confirmed_west_prince_potatoes>,
<http://www.agannex.com/diseases/the-latest-on-late-blight> and <http://www.agannex.com/production/new-strains-of-late-blight-dominating-canadian-potato-fields>
_P. infestans_ taxonomy:
<http://www.indexfungorum.org/Names/NamesRecord.asp?RecordID=232148>
Global Initiative on Late Blight:
<https://research.cip.cgiar.org/confluence/display/GILBWEB/Home>
- Mod.DHA]
[See Also:
Late blight, potato - Bangladesh: (KH) 20140320.2345850
2013
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Late blight, tomato - Oman: (BS) 20130603.1752356 Yellow leaf curl & blights, tomato - Pakistan: (SD) 20130206.1531086 Late blight, potato: new strains threat 20130111.1492024
2012
----
Late blight, potato - UK: strain Green 33 20120202.1031230
2010
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Late blight type A2, potato - Estonia: 1st report 20101129.4298 Late blight, seed potato, tomato - India: (HP) 20101015.3738 Late blight, tomato - Canada: (AB) 20100915.3336 Late blight & mildew, vegetables - USA, Canada, update 20100712.2328 Late blight, potato - Ireland: strain Pink 6 20100604.1851 Dickeya, leaf blights, potato - UK, Ireland 20100528.1775 Late blight, tomato - USA: alert 20100519.1648 Late blight, potato - India: (KA) control 20100505.1458 Late blight, potato - Ireland: strain Blue13 20100212.0505 Late blight, potato - Bangladesh: (RJ) 20100126.0285 and older items in the archives]
Topics
Species
